Telegraphy



TELEGRAPHY Filed April 25, 1942 3 Sheets-Sheet l N Q N NVENTOR LPH W EUA/757540 ATTORNEY July 23, 1946..

CHANNEL/4 R. W. BUMSTEAD TELEGRAPHY Filed April 25, 1942 FROM F/G.

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INVENTOR RALPH W. BUN/87540 ATTORNEY R. w. BUMSTEAD TELEGRAPHY Filed April 25, 1942 July z3, 1946.

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RS.. QU S INVENTOR RALPH W. @gl/45 71E/1D BY ATTORN EY Patented July 23, 1946 TELEGRAPHY Ralph W. Bumstead, Westfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application April 25, 1942, Serial No. 440,455

This invention relates to a novel system of telegraphy which is especially useful on radio communications channels for controlling printing telegraph apparatus of more or less conventional design. The system is also suitable for the transmission of intelligence on Wire lines and submarine cables.

It is an object of my invention to provide a system for use with a novel telegraph code having capabilities for dependable transmission of a relatively high number of words per minute.

A second object is to provide a printer control circuit operable in `response to the reception of variable length code signals in which the code elements are also of variable length.

A third object is to provide a start-stop printer control system operable in response to continuously transmitted signals.

A fourth object is to provide an electronic device to be controlled by incoming code signals of variable length for actuating a type-selector mechanism in a printer.

A fifth object is to provide a signal code converter responsive to variable length signals and capable of controlling the code selector members of a printer, or re-transmitting unit.

A sixth object is to provide a telegraph system for use with a signal code having certain characteristics which are favorable to privacy of communication.

A seventh object is to provide a multiplex system such that character selection is accomplished by means of a three-element signal code.

An eighth object is to provide a multiplex system for the transmission of intelligence by means of code signals which are not easily decipherable by unauthorized recipients.

A ninth object is to provide a radio telegraph system possessing inherent capabilities for the detection of errors due to the reception of mutilated signals.

The foregoing objects and other objects of my invention will be made apparent in the following detailed description. This description is accompanied by drawings in which:

Fig. 1 shows diagrammatically a circuit arrangement including an electronic distributor for successively applying the elements of the code signals to different code interpreting relays, these relays and their circuit connections being also ceiving apparatus assembly, and

24 Claims. (Cl. 1753-61) Fig. 4 shows a diagram of a novel signalling code which I preferably use in connection with the telegraph apparatus of this invention.

I refer rst to Fig. 3 while supplying a brief description of the fun-damental features of my invention and the mode of operation thereof. Assuming rst that the intelligence is to be transmitted over a 'radio channel and that multiplex transmission provides for the intermeshing of code signals for two distinct messages, these signals may be received on an antenna I and sensed by a radio receiver 2. The output from the radio receiver may first be passed to a signal regenerator 3 where any deformations of the wave components may be re-shaped. The regenerator delivers substantially a square Wave output. Accordingly, the output leads from the signal regenerator 3 may be caused to produce a reversible voltage on the load resistor R1 which has a grounded center-tap. Let it be assumed that when the upper output lead of the signal regenerator 3 is positive, that the square peak of the output wave then represents a marking impulse. On the other hand, when the lower one of the output leads from the signal regenerator 3 is positive, this condition represents a spacing impulse.

The marking impulses are applied to capacitors 4, 6, and 8 for controlling certain gaseous discharge tubes in the unit I0 which I term an electronic stepping commutator. The impulses representing spacing conditions will, however, be applied to the capacitors 5, l, and 9 which control other gaseous discharge tubes of this commutator in the unit Ill. Electronic commutators are well known in the art and may, as in the present embodiment, be of the gaseous -discharge type. The commutator I0 differs from ordinary rotary distributors and other cyclically operated switching mechanisms by virtue of the irregularity with which successive steps may be taken. ln other words, marking and spacing element/s of variable duration must be capable of stepping the commutator from one to a successive point at irregular time intervals.

Six output leads are shown at the bottom margin of the electronic commutator IU. Three of these are associated with a code interpreting relay unit Il which is appropriate to intelligence channel A. The three remaining output leads from the commutator I0 are connected to suitable relays inthe unit l2 for interpreting the signals appropriate to intelligence channel B.

The code interpreting relays of units ll and I2 depend `for their operation upon the automatic control of certain code element timers i3. In the pre-sent embodiment, where two printers and B are to be actuated in response to multiu pleX signals, six code element timer units are provided, three for each printer. They are respectively labelled, therefore, Al, A2, and A3 for printer A; and Bl, B2, and B3 for printer B.

The unit lll represents printer A and is shown having six input leads each of which controls conventional code yselector magnet in a printer of well-known type. These input leads carry impulses Which derive from contacts on the code interpreting relays. Correspondingly, printer B has six input leads, each for the control of its code selector magnets, and impulses carried by these leads derive from the contacts of relays in the channel B unit l2.

Printer A possesses a printer control magnet l5 which is in circuit with a particular one of the output leads from the electronic stepping commutator lil. This particular lead initiates an impulse at the mid-point of interpreting a code signal for channel Hence, the operation of printer A following a code selection takes place while coole selection is under way for channel B. Similarly, the printer control magnet Il for printer B is in circuit with a particular output lead from the commutator lil which is also used to decodeV the signals for channel A, Hences the operation of printer B is timed to be coincident with the interpretation of a channel A code signal. This arrangement permits continuous reception of alternate code signals for the two channels and also permits each printer to operlate after the code combinations have been set up in its code selecting magnets,

In carrying out my invention I propose to utilise existing facilities with obvious modifications for keying the signals automatically at the transmitter. are represented b-y a succession of two conditions, a marl; and a space, The character code signals, however, are preferably composed in accordance with different combinations of signal elements all of which are of dot length or multiples of the time interval occupied by a dot. Fig. 4 shows an arbitrary chart of code element combinations. Each marking or spacing element is'variable between one and four unit lengths or bauds as they are conventionally termed.

The term baud as employed in this specification and in the claims is in accordance with generally accepted terminology, as shown, for example, in an article by J. L. Callahan, R. El, Mathes Yand A. Kahn published in the January 1938 issue of Proceedings of the I. R. E. Quoting from that article: The baud (named after Baudot, the inventer 0f the five unit equal-length printer code that carries his name) is the shortest duration of a mark or space element in a given telegraphic code. All other marks or spaces comprising the code are integral multiples thereof.

It is essential to the carrying out of my invention that the code to be used shall be composed of marking and spacing elements each of which is commensurate with a baud or an integral number of bauds rlhis is true because, irrespective of the signaling speed, the cadence of the signals must be maintained constant. For economy of line time it is preferable to arrange the code signals so that those of shortest length shall be assigned to the most frequently occurring characters.

An analysis of a large sample of telegraph text shows that the word-space character and the let- As in most telegraph codes the signals ters of the alphabet should be arranged in the order appearing in Fig. 4 for maximum economy of line time. The space between words is more frequently used than any letter character. The letters E, O, and A occur most frequently. The letters X, J, Q, and Z occur least frequently. Other letters of the alphabet occur with more or less frequency and may, therefore, be assigned to code element combinations of variable length depending upon their frequency of occurrence in ordinary text.

In the chart of Fig. 4, and as mentioned above, it will be observed that each complete character signal is composed of three variable length elements, The first and last of these elements possess the same characteristic and the middle element possesses a different characteristic. When the first and last elements are markingf then the intervening element is spacing Alternately tranen itted character signals are intended to be so characterized. The intervening character signals are inverted. That is to say, the first and last elements thereof are spacing signals and the middle element is a marking signal.

In a two-channel multiplex system switching from one channel to the other may take place after each character code combination has been transmitted. The character signals for message A may. if desired, be composed of code elements of which the rst and last are marking. For message B, however, the rst and last elements of each character code will then be spacing. Hence the line of separation between the end of a message A character code signal and the commencement of a message B character code signal will always be indicated by a polarity reversal. Two other polarity reversals also occur in the body of each character code signal and these are not distinguishable from the ones rst mentioned, The receiving apparatus must, therefore, be brought in step with the transmitter in order to decode the intelligence. The mutilation of one code signal automatically throws the decoders out of step for further transmission, and reception then being completely garbled, an error cannot go unnoticed. Re-phasing of the decoders is a simple matter which will be hereinafter explained.

By alternating the code combinations as between marking and spacing elements in successive character code signals, it is possible to effect continuous transmission of significant code elements without any loss of time for meaningless spacing between the code signals. The present system, therefore, bears certain resemblances to that of United States Patent No. 1,187,035 which was granted June 13, 1916 jointly to Albert H. Bumstead and to myself. In that patent we disclosed a system wherein each code signal consisted of a marking element of variable duration followed by a spacing element of variable duration. In order to improve upon the eiciency of code signal transmission, the number of code elements in each signal is now increased from two to three and the length of each code element is reduced from six to four degrees of variability.

The more complete diagram of Fig. l will now be referred to in giving a full explanation of the circuit arrangement. This diagram should, however, be viewed by placing it over Fig. 2 in such manner that any one of the groups of four wires each' leading to the bottom margin may be matched against a single group of four wires at the top margin of Fig. 2. In Fig. 2, the circuit arrangement shown may be applied as though duplicated, for each one of the groups of four output wires from Fig. 1.

In Fig. 1, I show six gaseous discharge tubes, TI, T2, T3, T4, T5, and T6. Each of th'ese tubes is arranged to respond in succession to marking and spacing units of the received signals. It is well known in the art that such tubes may be interconnected in such manner that when a rst tube is ignited, it will remain conductive until a succeeding signal ignites the second one. At that instant, the previously ignited tube becomes extinguished and the ignited second tube prepares a condition for the next succeeding signal to ignite the third tube. I-Iowever, the steps of progress in the successive ignition of these tubes may be of variable duration, and in order to measure the time intervals between successive igniticns, I employ a further electronic system as shown in Fig. 2, consisting of three gaseous discharge tubes T'I, T8, and T9.

I will now describe more completely th'e circuit arrangement which includes the gaseous tubes TI to T6 inclusive.

The gaseous discharge tube TI has an input circuit which includes a cathode, a biasing source 2|, and a resistor R2I connected to its control grid. Also connected to this control grid is a resistor RI through which a signal impulse may be passed across a capacitor 4 and in certain instances across capacitor C1. The latter is used at moments of depression of the key 24 for phasing purposes at the outset of reception.

I'he grid of tube TI also has a connection through resistor RI I and uni-directional conductor 22 to the cathode of tube T6. The purpose of this connection is to neutralize the negative bias from the source 2| during the time of ignition of tube T6 and in anticipation of the ring of tube TI. The positive potential from the cathode of tube T6 does not in itself produce a sufficient potential drop across resistors RII and R2I to lire the tube TI, but when this grid bias is further reduced by the signal, th'en, and then only, is the negative potential from source 2I suilciently overcome to produce ionization in the tube TI.

Each of the tubes TI-TG possesses an output circuit which includes the grounded source 25, one of the resistors RI'I, RIB, RIS, R21, R28, or R29 each appropriate to the anode of a respective tube, and a cathode resistor R8 to ground.

'I'he cathode of each of these tubes is also connected to other circuits which are parallel to resistor R8. In the case of tube TI, these parallel circuits are completed at different times through the windings of relays 5I and 52, the times of circuit closure being dependent upon the operation of the code element timers of Fig. 2. For the tube TI` the entire circuit arrangement of Fig. 2 is comprehended in the one unit I3 which in Fig. 3 is designated AI. Each of the alternative circuits through the windings of relays 5I and 52 returns to ground through a different one of the gaseous discharge tubes TI, T8, and T9 (Fig. 2).

The input and output circuits of tubes TZ-T are exactly the same as described above in reference to the tube TI. In order that tube TI may be extinguished at the moment of firing tube T2, a surge impulse is caused to be impressed Vacross capacitor CI which interconnects the two anodes of these tubes. This device for extinguishing one tube when another is fired is well known in the art. For example, it is shown in Patent No. 2,252,364, issued August 12, 1941, to C. R. Clark, that the anodes of two gaseous tubes V4 and Ve may be intercoupled by a capacitor Cs for the purpose of causing each tube when it res to extinguish the other. The operation is described in the Clark patent on page 3, column 1, lines 64-67. Similarly capacitors C2, C3, C4, C5, and C6 interconnect diierent pairs of anodes in the tubes TI--T' so that successive firing of these tubes will always result in extinguishing the glow of the previously red tube.

Tube T2 is prepared for firing by the previously ignited tube TI, which' produces a potential drop through the uni-directional conductor 22, resistors RI 2, and R22, the biasing source 2 I (for tube T2), and thence to ground through resistor R8 appropriate to the cathode of tube T2.

In the same manner, preparatory conditioning circuits are shown for tubes T3-T5 which include the following elements: between the cathodes of tubes T2 and T3 there is a uni-directional conductor 22, resistors RIS and R23 and a separate biasing source 2l. 'I'h'e grid of tube T3 is connected to the junction between RIS and R23 and is also connected to capacitor 6 through R3 for receiving a control signal.

Capacitor 'I and resistors R4, RI4, and R24 are appropriate to the control grid of tube T4. Capacitor 8 and resistors R5, RI5, and R25 are appropriate to the grid of tube T5. Capacitor 9 and resistors R6, RIG, and R26 are appropriate to the grid of tube T6. The circuits are exactly similar for each tube and, therefore, need not be further described.

It will be clear from the above description that when marking impulses are impressed on capacitors 4, 6, and 8 simultaneously, only one of the tubes TI, T3, or T5 will be ignited, depending upon which of the tubes T6, T2, or T4 was previously ignited. Similarly, in response to the reception of a spacing impulse impressed simultaneously on capacitors 5, 1, and 9, a single one of th'e tubes T2, T4, and T6 will be ignited, depending upon which of the tubes TI, T3, or T5 was previously ignited. Hence, the succession of marking and spacing impulses produces a stepby-step ring of the tubes TI-TB in the order in which they are numbered. Each of the relays 5I--62 inclusive possesses one or two windings as shown. Each winding when energized is sufficient by itself to pull up the relay armature. The winding of relay 5I connects through conductor I8 to th'e anode of tube T'I. The left hand winding of relay 52 is connected through conductor I9 t0 the anode of tube T8. The right hand winding of relay 52 is connected through conductor 20 to the anode of tube T9.

During the reception of a marking signal of two or more bauds, as measured by the ionization of tube TI, the code element timers as shown in Fig. 2 may be sequentially actuated so that relay 5I will operate rst, and, While it holds, the left winding of relay 52 energizes. If the signal is of four bauds length, the maximum, then relay 5I and the left winding of relay 52 `will de-energize, but relay 52 will still be held by the energization of its right winding.

Although the tubes TI, T8, and T9 may be ignited successively in response to the firing of tube TI, the code element timer devices are automatically extinguished by the extinction of tube TI since they derive their anode potential through the space path of tube TI. I will now describe the code element timer circuit arrangement of Fig. 2, and, in so doing, I wish it to be understood that this circuit is duplicated in association of each one of the tubes TI-T6.

lTube T1 has an input `circuit which includes resis-tors R3I and R32 and the biasing source |07, all Pbetween the cathode and the control grid. Resistor R32 is shunted by capacitor Cf'. I, thus forming a time constant circuit for controlling the n ring of tube T1 after it receives a Vcontrol impulse from tap |04 on resistor R8; this tap being connected to the conductor 23 and thence to the grid of tube T1 through source im'. The value of the time constant elements R32 and C4| provides a delay equal to substantially one and -one half bauds. Tube T'| cannot, therefore, be ignited until after the termination -of a marking signal of one baud length.

The tube T8 is fired after a delay equal to one baud subsequent to the moment of ring tube Tl. This result is obtained by causing a potential drop through resistors R33 and capacitor CA2 to ground. The input circuit for tube T8 includes a cathode resistor R34, capacitor C42, and biasing source HU. The time constant value of resistor R33 and capacitor lC42 is suitably determined for producing a delay equal to one baud in the tiring of tube T8.

Tube T9 likewise has an input circuit 'which includes a cathode resistor R36 connected to ground, capacitor C43, and the biasing source H3. Between the positive terminal of source H3 and cathode of tube T6 is connected a resistor R35 across which a suitable potential drop occurs when tube T8 is fired. This potential drop charges capacitor C43 to a point where it overcomes the negative bias of source 'I i3 on the grid of tube T9, thus causing this tube to be red after a delay of one baud following the ignition of tube TS.

Although all of the tubes Tl, T8, and T9 are extinguished simultaneously with the extinction of tube Tl, it is also necessary to extinguish tubes Tl and T8 when tube T9 is red. Tl is extinguished by the capacitive connection through C between the cathodes of the tubes Tl and T9. Tube T8 is extinguished, however, by a capacitive connection through C45 between the anodes of these tubes. Extinction of tubes T`| and T8 by surge impulses across capacitors C135 and C411 is thus caused in the `well-known manner.

I will now show how any one of four permutations in the energization of the relays 5| and 52 .may result from the non-firing or the successive firing of tubes T1, T8, and T9.

It will be appreciated by those skilled in the art that my invention may be used in association with various `forms of printing telegraph apparatus or with other selective devices which are capable of operation in response to code signals. Conventional printers are arranged to obtain type bar selections from the permutational setting of a series of code bars. While such code bars rhave not been herein shown nor described, it `will be understood that they may be readily actuated by means of a series of individual selector magnets of the series llld as shown in the blocks for printer A and printer B respectively. See Fig. 1. It will also be understood that my invention is not limited in its scope to Selective mechanisms which would necessitate the use of printer code bars. On the contrary, any device which is to be remotely controlled by means of code signals could be usefully employed Where the interpretation of code signals is required.

Certain permutations of the code selector magnets lll-d5, inclusive, in printer A require that neither of the magnets 4| nor 42 shall be energized. This permutation is obtained by a marking signal of one baud length. The one baud being Vless than the time constant value of capacitor C4| in shunt with resistor R32,none-of the tubes Tl, TS, nor TS will be ignited bef-ore tube Tl becomes extinguished.

In order to energize code selector magnet 4|, it is necessary that relay 5| alone be energized. This is accomplished by a marking signal of two bauds duration. In this case tube T1 is ignited, but the time constant value of resistor R33 and capacitor C causes a delay in the ignition of tube T8 beyond the duration of the two baud signal. Hence relay 5| will be energized, but relay 52 will not be energized. The pulling up-of the armature 3| prepares a circuit through selector magnet 4i alone.

Assume now that the length of the signal is three bauds. Both tubes T`| and T8 will be ignited and hence the two relays 5l and 52 will `be energized. The closing of armatures 3| and 32 against their contacts prepares for the energization of selector magnets 4| and 42. This condition, therefore, corresponds to a third permutation of the two code selector magnets 4| and 42.

The fourth permutation requires code selector magnet 42 alone to be energized. This is accomplished by the firing of tube T5 and the resultant extinguishing of tubes Tl and TS. The space path through tube TQ is fed with potential from tube Tl through the right hand winding only of relay 52 and thence through conductor 20 to the anode of tube T9. As previously stated, the firing of tube T9 causes the extinction of tubes T1 and T8. Hence, the code selector magnet 42 alone becomes energized.

In considering the operation of relays 5| and 52 and their effects upon the code selector magnets 4| and 62, it should be understood that neither of these magnets is energized merely by closing armatures 3| and 532 against their front contacts, because these front contacts themselves are not energized until the iiring of tube T2. The relays 5| and 52 are suitably designed to hold their armatures against the iront contacts for a brief moment at the instant of firing tube T2 and before the tube TI becomes completely deionized.

The front contacts of armatures 3| and 32 are connected directly to the cathode of tube, T2 through conductor 26.

When tube T2 becomes ignited in response to the reception of a spacing signal, the same operation of the code element timers of Fig. 2 is repeated for measuring the number of bauds in this spacing signal. As a result of such operation, a permutational selection and energization of code selector magnets 43 and 44 takes place. Any one of four permutations is obtained as a result of measuring the duration of a spacing element which varies between one and four bauds in length. The code selector magnets 43 and 441 are similarly controlled by relays 53 and 54 in the manner explained hereinabove with respect to code selector magnets il and i2.

The cooperation of tube T3, relays 55 and 56, and their armatures 3| and 32 respectively in controlling the permutational selection of magnets 45 and 4S will also be understood in view of the foregoing description. It will be clear from the above also that printer A receives a complete permutational set-up of its selector magnets as a result of successive ring of tubes TI, T2, and T3.

The operation of the printer magnet I6 for setting in motion the type printing mechanism depends, however, upon the moment of ring of tube T5, which is in the group appropriate to the selection of code permutations for printer B.

VThe control circuit for printer magnet I6 is,

therefore, connected to the cathode of tube T through conductor 21.

It is not necessary to trace the circuits which include the relays 51--62 inclusive and the code selector magnets appropriate to printer B in view of the foregoing description of similar circuits appropriate to the printer A. It should be noted, however, that the printer control magnet l1 in printer B is connected through conductor 28 to the cathode of tube T2 so that its actuation may follow the successive steps of operation of the tubes T4, T5, and T6 and the permutational selection of the code selecting magnets lll-4S in printer B.

Operation Inprder to better understand the sequence of operations which take place upon reception of a single character signal, the code signal for letter i K has been chosen to illustrate successive activations of the different discharge tubes and the .consequent selective functions which are performed thereby. In the following table different symbols are disposed in the several lines to repre- `sent a horizontal time scale which measures the Vbauds of the code signal.

As shown in Fig.' 4, the code signal for letter K when transmitted on channel A comprises a first marking element having the duration of four J bauds followed by a'spacing element having the duration of two bauds and ending with a onebaud marking element. v

Line (a) gives the numbers of the bauds in the time scale.

Line (b) shows the code signal itself expressed by means of the letter M for marking bauds and the letter S for spacing bauds.

Line (c) shows the times when diiferent tubes of Fig. l are activated, the letter T being omitted from the references. That is to say, up until the commencement of the code signal in questiongtube TE will be understood to be conductive. This tube is extinguished upon the initiation of the marking element at the commencement of `the code signal assigned to channel A.

At this instant tube Tl (abbreviated I) is ignited. The ignition state lasts for four bauds. Tube T2 is ignited at the commencement of the spacing element and remains ignited for a period of two bauds. Tube T3 is ignited for a period of one Ibaud and is extinguished upon reception vof a spacing element appropriate to a code signal in channel B. This code signal pertains to responses Ain tubes T4, T5, and T6.

During the conductive period -of tube Tl, and up until the nrst baud is completed, the time constant device comprising resistor R32 and capacitor 4Clll in the input circuit of tube T1 delays the activation of tube T1 until the commencement of F At the commencement of the time baud, tube to* be selected.

I T8 becomes ignited, the neecssary delay being obtained by means of the time constant circuit which includes resistor R33 and capacitor C42.

Likewise tube T9 is activated during the fourth mind that the printer magnet selections lare obtained by circuit closures through the armatures of relays such as 5l and 52 and that with respect to relays 5l and 52, such circuit closures are made at the instant of rendering tube T2 conductive, it will be seen that no printer magnet selection results from the'actuation and release of relay 5l. With respect to the operation of relay 52, however, its windings are successively energized `and this relay holds its armature until tube T2is activated. Hence, `printer magnet 42 is selected. If the` length of the marking element in question had been onlythree bauds instead of four; then relay 5I would notvhave been released vand both printer magnets 4| and 42r would have been selected. v K Y Referring to line (f) ofthe above table, it will be observedthat relay 53 is energized at thel initiation of the second spacing baud, which is baud 6. The time constant circuit for tube T1 in connection with the relay 53 does not permit tube T1 to ignite during the first spacing baud, which is baud 5.

y But this spacing element extends through two bauds and causes printer` magnet 43 The marking element which terminates the 'code signal and is restricted to baud 1 is ofinsufficient duration to activate tube T1 when regarded as in series with relay 55. This relay, therefore, remains un-energized and no printer magnet selection takes place in respect thereto.

The overall effect of'- operation of the tubes and relays as above described in response to thereception of the code signal for letter K is to cause printer magnets 42 and 43 to be selected. This selection would representa permutation suitable for printing the character"K.

Other operations in'respect to the selection of printer magnets for the remaining letters of the alphabet and'for other characters may be readily understood in View of the foregoing.

' In describing my invention as above, I havein- -cidentally brought out the functions of the various elements 'of receiving apparatus so that the operation of the system as a whole may be readily understood. Certain details of operating'procedure have 'only been slightly touched upon, however, and while these may not in all cases'be essentiall to the carrying out of the invention, it may be well to discuss-them in more detail.

Manipulation of the phasing key 24 is to be understood as necessary only at the commencement of message reception, or in case the signals loecome mutilated so as to throw thedistributor out of phase. This key 24 is used'f'or bringing the electronic switching system comprising tubes TI--TE in step 4with the received signals." It-is obvious that if a character signal were to start by igniting tube T3, then a portion of the character signal would be allocated to printer A while anl l other portion thereof would be allocated to printer B. Furthermore, the rst element of a character signal must not be caused to excite either of the tubes T3 or T5. By depressing the key 24 momentarily, it is possible to arrest the consecutive exci-` tation of the tubes in the system TI-T6 after TI has been ignited, since both marking and spacing impulses are then applied to the grid of tube Tl, and no spacing impulses can reach the grid of tube T2. But, at the instant of key depression, one of the tubes T2 to T6 inclusive may have been ignited. The signals Will, therefore, advance the electronic switching step by step as far as Tl. Thereafter during depression of key 24, subsequent spacing and marking signals will have no elTect. But upon release Of key 24, the next succeeding space signal will traverse capacitor 5 for igniting tube T2. If such operation fails to start tube T2 in proper phase -with a character signal for channel A', then the key should be depressed again. The chances are one in three that any attempt will be successful. During this trial period, suitable test signals should be sent. For example, the signal for F" would be quite suitable since it has three elements which are distinguished by lengths of one, two, and three bauds respectively. If a succession of Fs is transmitted on channels A and B, they will be transcribed as Ys under one condition of dephasing and as Hs under the condition of dephasing of the distributor.

I have not disclosed nor discussed in the foregoing part of this specification any details of a transmitting apparatus which might be suitably arranged and send out character signals of the type vshowin in Fig. 4. Perforated tape transmitters of various designs are well known in the art and thosewhich have a magnetic tape feedmechanism, as in start-stop transmitters, may readily be adapted to the present system. It should be understood, however, that where this system is used for two-channel multiplexing, the terminating baud of a character signal in one tape may be rendered effective to start transmission of one character signal in the alternate tapev and viceversa. acter are arranged transversely of the tape, as is usual, then the duration of each marking-or spacing impulse may be denoted by the distance of a perforation from a longitudinal reference line, say the row of sprocket holes for the feeding of the tape. Both marking and spacing elements of the code signal may be perforated in any of four positions in the tape according to the length of the signalling element. Hence, with the threeelement code signal, `twelve parallel rows of perforations will be made, but only three perforations will existv in each sending position. The tape itself is to be driven step by step from one scanning position to another and the stepwise motion will be at irregular intervals depending upon the number of bauds in each character signal. The technique of tape transmission as conventionally practiced requires only slight modifications in order to adapt it for the transmission of unequal length code signals in the manner above suggested.

Recapz'tulation In the foregoing description, I have shown how the .received signals .may be applied first to the operation of an electronic switching system, each tube of which is ignited in succession. The ignition of one tube extinguishes. the previously ignited tube. During .the ignition of any single tube, the number of bauds of a marking or spac- If the tape perforations for each charing element is counted by means of a system of three gaseous discharge tubes the space paths of which are in circuit with a pair of selecting relays. The closure of selecting circuits under control of these relays is timed at the moment of transition from one to the next conductive state of the gaseous discharge tubes in the electronic distributor. Three of the latter tubes are used in making character selections by means of the control of six code selector magnets in printer A. After a particular code combination has been set up in these six selector magnets, printer A is caused to o-perate for printing the character. The printing operation takes place while the selection of code combinations is being made with respect to printer B. Likewise the printing operation in printer B takes place during the next succeeding,r selectingl operation appropriate to printer A.

The decoding of messages which are transmitted by means of the signal code herein shown would be quite dinicult if attempted by unauthorized persons. Assuming that it is not knownvhow these code signals are composed, they might, of course, be received on an ordinary tape recorder. If separated into combinations of uniform length they would convey no intelligence whatsoever. The fact that the same character is represented part of the time by a transposed code combination would also be confusing. There is n0 space separation between character signals. There is no uniformity of marking elements for the characters. One signal consists of two marking elements separated by a spacing element, and the next succeeding signal is represented by a single marking flanked by two spacing elements.

If, however, it is desired to increase the cryptographic nature of the transmission, certain further transposing methods may be adopted. These are well known in the art and need not be discussed in detail. It is a well established practice to provide either a periodic -reversal of the signal polarities or else the reversals can be made in a random manner by means of a cypher tape which is Produced in duplicate, and only the transmitter and the authorized receiver possess the two copies. Without one of these duplicate tapes, it isl impossible to decode a transmitted signal.

I have stated in the objects of the invention that the system lends itself to the detection of errors when the signals are transmitted over a radio channel and may become mutilated. It is apparent that such mutilation of the signals as in the splitting of a single marking element into two mark-ing elements would throw the electronic distributor out of step. Thereafter. until the distributor is again phase-corrected, each character would. straddle the tWo multiplex channels at the receiver. This condition would immediately be noticed by the receiving attendant who would then call for re-transmission of as much of the transcription as may have been mutilated and such transcription would naturally commence with test signals during which the electronic dis.- tributor would be newly phased.

Various modifications of vthis invention may suggest themselves to those skilled in the art. The scope of the invention is, therefore, limited only in accordance with the scope of the claims.

I claim:

1. In a telegraph system, the method of utilizing alternate marking and spacing elements to formulate the code combinations for each letter of the alphabet and every other character, which comprises starting and ending each such code combination with like elements, interposing a 13 single element of opposite sense between said like elements, and instantly following one code combination by another, the sense of corresponding elements in two successive code combinations being always reversed.

2. The method of selecting the code bars of a telegraph printer which comprises applying a first selection simultaneously and permutationally to two of said code bars, applying succeeding selections in the same manner to diierent pairs of code bars, and causing each pair-selection to result from timing the duration of a single element of a signal code combination.

3. Telegraph signal decoding and type printing apparatus operable in response to signals of unequal length, said apparatus comprising a set of magnetically actuated character selectors, relay means for producing a permutational setting of said character selectors by their magnets such that a character corresponding to a received code signal is caused to be printed, means for timing each of three successive elements of said signal, and an electronic distributor responsive to alter.. nate marking and spacing elements of said code signal, and arranged for stepwise advancement through successive stages with each shift in the sense of said signal elements, said timing means and said distributor being jointly operative to control said relay means.

4. Apparatus according to claim 3 wherein two printers are provided, and said distributor comprises means for allocating successive complete code signals alternately to each printer.

5. In a telegraph system, the combination of a distributor for receiving code signals of unequal 1 length, means in said distributor for subjecting the same to stepwise advancement through successive stages with each shift in thesense of the signal elements of which said code signals are composed, means for individually timing said signal elements, and type printing apparatus operable in accordance With the character signicance of said signals as translated by said timing means in cooperation `with said distributor.

6. The combination according to claim 5 and including a plurality of gaseous discharge tubes in said distributor, and means including circuit elements and a source of operating potentials connected to the electrodes of said tubes in such manner that said stepwise advancement is characterized by the successive ring of individual tubes in different stages, and the extinction of the discharge in the tube previously red.

7. The combination according to claim 5 and including a plurality of gaseous discharge tubes in said timing means, and means including timeconstant circuit elements and a source of operating potentials connected to the electrodes of said tubes in such manner that one of said tubes is fired after a predetermined time `interval following a stepwise advancement of said distributor, and others of said tubes are fired in periodic succession during the lapse of time between successive stepwise advancements of said distributor, the number of tubes so fired corresponding with the number of bauds, less one, which are comprehended in a given signal element.

8. In a telegraph system, a distributor comprising a plurality of gaseous discharge tubes, an operating potential source and circuit parameters -for said tubes arranged to ignite the same in a predetermined sequence under control of alternate marking and spacing impulses of received code signals, and timing means operl4 able in response to the ignition of each of said tubes for counting the number of bauds in each of the elements of said code signals.

9. In a telegraph system, a distributor comprising a plurality of gaseous discharge tubes, an operating potential source and circuit parameters for said tubes arranged to ignite the same in a predetermined sequence under control of alternate marking and spacing impulses of received code signals, a plurality of parallel-arranged circuits connected between an output electrode of each said tube and said operating potential source, and inertialess switching means for closing certain of said circuits successively in dependence upon the duration of the discharge in a given one of said discharge tubes.

10. In a device of the class described, a plurality of gaseous discharge tubes each controllably coupled to a source of marking and spacing telegraph signals which are transmitted at a definite baud frequency, a direct current operating potential source for said tubes, a cathode resistor connected between each of said tubes and the negative terminal of said directv current source, means including circuit parameters for said tubes whereby the tubes are ignited one at a time in a predetermined sequence in step with each shift in the sense of the signal elements, a plurality of relays, inertialess circuit closing means individual to each relay Winding circuit, a plurality of said winding circuits being in shunt with each said cathode resistor, and time constant control means effective to successively operate said circuit closing means at a rate corresponding to the lbaud frequency of said signals.

11. The combination according to claim 10 and including telegraph signal translating means operable by the contacts of said relays.

12. In a device of the class described, an inertialess distributor comprising a plurality of parallel circuits each including the space path of an individual gaseous discharge tube, input circuits for the several tubes arranged to receive signal impulses, means for pre-conditioning each said input circuit in succession for causing its respective tube to strike upon the arrival of a given signal impulse, means for extinguishing each tube upon the striking of the succeeding tube, and signal translating and decoding means in series with said space paths.

13. The combination according to claim 12 and including a plurality of relays in said signal translating and decoding means, and means for closing the winding circuits of said relays selectively in dependence upon the duration of a particular discharge in one of the tubes of said distributor.

14. A system for translating code signals into selective effects comprising a series of gaseous discharge tubes arranged for successive ignition in response to sense shifts in a train of telegraph signals, an operating potential source connected through different branch circuits which include the output electrodes of said tubes, said branch circuits including a cathode resistor individual to each tube and a plurality of relay windings in shunt with each cathode resistor, and means including other gaseous discharge tubes having output circuits which are series-connected to said relay windings for producing permutational relay circuit closures in dependence upon the significance of said code signals.

15. A system according to claim 14 and including a type printer having type selective means permutationally operable in accordance with said relay circuit closures.

16. A system according to claim 14 and including time constant circuits associated with said other gaseous discharge tubes whereby the latter are caused to be ignited in predetermined sequences.

17. Apparatus for decoding character code signals comprising an electronic distributor of the aperiodic type, said distributor including a series of discharge devices adapted and arranged for sequential activation in accordance with senseshifts in a train of said signals, a plural-ity of parallel-connected circuits arranged in sets, each set being in series with the space path of a respective one of said discharge devices, code-interpreting means in each of said circuits, and time constant means operably associated with each of said circuits whereby the signiiicance of each character code signal is determined.

18. In a telegraph receiving system for effecting character selection by response to character code signals each composed of three variable length code elements the rst and last of which `are always alike in sense, the method of independently controlling each of siX selector units in a, selecting mechanism in such manner that a different permutational arrangement of said selector units is provided for each character selection, said method comprising grouping said selector units in three pairs, producing a selective response in one, the other, both, or neither of the selector units of the rst pair in accordance with the length of the first code element, and producing selective responses in like manner in the second and third pairs of selector units in accordance with the respective lengths of the second and third code elements of said character code signals.

19. The method according to claim 18 and including the step of inverting the sense of the variable length code elements in successive character code signals, whereby a Character Code signal containing a rst and third element of marking significance is always followed by a character code signal containing a irst and third element of spacing signicance.

20. Apparatus for receiving and decoding signals comprising a plurality of translating devices, means for grouping variable length code 16 elements as successively received into groups of three, the rst and last of which are always alike in sense, and means for assigning successive groups to dilerent translating devices, thereby to derive character signicance respecting a given alphabetical letter, gure, or other character from each group.

21. Apparatus comprising means for receiving and means for translating code signals wherein the composition of each character code combination is defined by a succession of three elements the first and last of which are always alike in sense, said elements being commensurate with one or an integral number of bauds, said translating apparatus including an electronic distributoi` for grouping the received code elements into threes, and timing means for counting the num ber of bauds in each element.

22. Telegraph receiving apparatus comprising means for utilizing alternate marking and spacing code elements of a signal train to translate the same into character symbols, each of said symbols being denoted by a group of three code elements, and each of said elements being com.- mensurate with from one to a certain integral number of bauds and means for assigning successive groups of signal code elements to different portions of said translating means thereby to allocate alternate groups of code elements to one such portion and intervening groups to another such portion, so that two multiplexed signal trains are translated into separate pieces of intelligence.

23. In a telegraph system which utilizes alternate marking and spacing elements and always three such elements to formulate a code combination for any letter of the` alphabet or other character, an electronic distributor for producing code element channel separation of the signals, means for measuring the duration of each code element in terms of bauds, and translating means for deriving a character signiiicance from each measured code combination.

24. In a device of the class described an electronic distributor comprising means for distributing successive signal elements of variable duration to respectively diierent translating channels, and means for measuring the duration of each signal element in terms of bauds.

RALPH W. BUMS'I'EAD. 

